sage.combinat.cluster_algebra_quiver: Modularization fixes for imports

Author: Matthias Koeppe

src/sage/combinat/cluster_algebra_quiver/all.py

@@ -15,3 +15,6 @@
 lazy_import("sage.combinat.cluster_algebra_quiver.quiver_mutation_type", "QuiverMutationType")
 lazy_import("sage.combinat.cluster_algebra_quiver.quiver", "ClusterQuiver")
 lazy_import("sage.combinat.cluster_algebra_quiver.cluster_seed", "ClusterSeed")
+
+del install_doc
+del lazy_import

src/sage/combinat/cluster_algebra_quiver/quiver.py

@@ -37,18 +37,18 @@
 #                  https://www.gnu.org/licenses/
 # ****************************************************************************
 
-from sage.structure.sage_object import SageObject
 from copy import copy
+
+from sage.structure.sage_object import SageObject
 from sage.rings.integer_ring import ZZ
 from sage.rings.infinity import infinity
 from sage.graphs.digraph import DiGraph
 from sage.graphs.graph import Graph
 from sage.graphs.views import EdgesView
 from sage.arith.misc import gcd
-from sage.modules.free_module_element import vector
-from sage.matrix.constructor import matrix
 from sage.categories.cartesian_product import cartesian_product
 from sage.misc.misc_c import prod
+from sage.misc.lazy_import import lazy_import
 from sage.rings.rational_field import QQ
 from sage.rings.polynomial.polynomial_ring import polygen
 from sage.combinat.cluster_algebra_quiver.quiver_mutation_type import QuiverMutationType, QuiverMutationType_Irreducible, QuiverMutationType_Reducible, _edge_list_to_matrix
@@ -57,6 +57,9 @@
 
 from sage.combinat.cluster_algebra_quiver.interact import cluster_interact
 
+lazy_import('sage.modules.free_module_element', 'vector')
+lazy_import('sage.matrix.constructor', 'matrix')
+
 
 class ClusterQuiver(SageObject):
     """